Former Denver Police detective Lt. Jon Priest displays three binders he kept in his office that comprised a synopsis of 75,000 documents stored in police archives that were collected during investigations from the 1991 United Bank robbery. (Denver Post file)

5:04 a.m., Father’s Day, 1991.

An alarm sounds in the hallway of the subbasement at the United Bank building — now Wells Fargo — at 17th Avenue and Lincoln Street in Denver.

Something or someone in a storage room on the subbasement level triggered the alarm.

A light appears on a board in a monitor room on the Concourse level, one floor below street level.

William Rogers McCullom Jr., 33, or Phillip Lee Mankoff, 41, presumably turns the alarm off, almost immediately. The alarm was never turned back on.

At 7:30 a.m., guards from Wells Fargo and Loomis Armored Inc. arrive at United Bank to make weekend deposits from stores, bars and restaurants. Because of holiday gift buying the bags of money are heavier than most weeks.

Then at 9:14 a.m., a man standing at a door where freight is delivered into the building buzzes the guards.

Kirk Mitchell is a general assignment reporter at The Denver Post who focuses on criminal justice stories. He began working at the newspaper in 1998, after writing for newspapers in Mesa, Ariz., and Twin Falls, Idaho, and The Associated Press in Salt Lake City. Mitchell first started writing the Cold Case blog in Fall 2007, in part because Colorado has more than 1,400 unsolved homicides.